The traditional means for advertising that a house is for sale or lease is by the placement of real estate signs at the front of the property. It is desirable that the signs are visible during high traffic times, which are often after sunset and before sunrise. The placement of the signs often precludes connection to conventional power sources such as outlets. A solar powered lighting system is a solution that has been suggested but still requires improvements for widespread acceptance. It is also desirable that the illumination can be turned off at specific hours. The ability to control the time that the illumination is on preserves battery life, is a courtesy to neighbors and may be required by local ordinance. Often the placement of the sign is not ideal for collection of solar energy. The ability to aim the solar photovoltaic collection panels independently of the light placement is an improvement. Non-ideal solar collection can also be mitigated by an improved power control system.
Doyle (U.S. Pat. No. 5,101,329) describes a lighting system for a real estate sign that clamps over the horizontal arm of the sign. Doyle provides no provisions for independently aiming the solar panels and no details for controlling the charging and discharging process. Tanner (U.S. Pat. No. 5,217,296) provides a lighting system to be attached to a flat wall and provides a means to independently aim the solar panels. However the control circuitry of Tanner is complicated and expensive. It requires separate circuitry for light sensing and battery and lamp control. Tanner does not provide means to control the lighting both before sunrise and after sunset. Tanner also does not provide for means to control the current or energy supplied to the lamps to prolong battery life. The mounting mechanism of Tanner would also not enable lockable attachment to a post. Giannone (U.S. Pat. No. 6,004,002) describes a complete real estate sign system including lighting. Although Giannone provides a solar panel that can be independently aimed, the system is not easily adapted to current signs without modification.
Typically the signs that are to be lighted are not located convenient to an electrical supply. Real Estate signs for example are often located at the front curb of the property far from convenient electrical outlets. There have been many systems advocating a battery powered system in which the batteries are recharged using electrical power from an associated photovoltaic solar panel. The challenge to implement such systems lies in designing a control system that will turn the lights on and off at the appropriate times, re-charge the batteries when solar energy is available, protect against over-charging the batteries to maintain battery life, protect against overheating batteries during the charging and discharging cycles, maximize utilization of the batteries available energy and prevent excessive discharge of the batteries such that the system is completely shutdown and control is lost and do all this with a minimum of electrical components to reduce cost. Schmidt (U.S. Pat. No. 6,028,694) describes an electronic control for LED's using a microcontroller and pulsed modulation for a power supply. However they do not describe an economical system. They include for example a switch mode power supply for current control. This task can more economically be accomplished with clever programming of the microcomputer.
There is a need for a portable solar lighting system that may be attached and securely locked to existing sign and post configurations without modification of the sign or post. There is a need to be able to lock the lighting system to the post using conventional padlocks to prevent theft. There is a need for a simplified control system for such lighting that will turn the lights on and off both after sunset and before sunrise, control the charge and discharge of the batteries in use and adjust the energy supplied to the lights to optimize battery life and illumination time. There is a need for a lighting system that can be flexibly aimed to light various portions of a sign attached to a post. A system is needed with the ability to aim the lighting to illuminate a top portion or attachment to a sign, a bottom portion or attachment to a sign and/or both. There is a need for a control system for a lighting system that will automatically determine the time of sunrise and sunset and program the duration of lighting of the sign relative to both sunset and sunrise.